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  • Autor: Thomas Mérő x
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Breeding birds of shelterbelts near Sombor (NW Serbia)

In 2008, breeding birds were studied in the shelterbelts surrounded by arable land NW of Sombor (Vojvodina, NW Serbia). Seven 500 m long sections of wooded shelterbelts were selected and surveyed for birds six times between May and July. Sampling plots differed in tree species composition and dominance, in height of trees, and presence and composition of shrub and herb layers. 22 breeding species were found with a mean density of 9.86 ± 1.47 pairs/km of shelterbelt. The mean number of species per shelterbelt was 8.3 ± 1.2. Species richness ranged from 4 (shelterbelt G) to 14 (shelterbelt D) species. Similarity, measured by the Sørensen index, showed strong qualitative similarity (over 70%) between the compared communities in only 19% of all possible pairs of shelterbelts. The most abundant breeding species were Golden Oriole Oriolus oriolus and Greenfinch Carduelis chloris, with overall linear densities of 2.9 and 2.6 pairs/km, respectively. Overall linear densities of a further four species (Red-backed Shrike Lanius collurio, Syrian Woodpecker Dendrocopos syriacus, Whitethroat Sylvia communis and Cuckoo Cuculus canorus) exceeded 1 pair/km. The densities of breeding birds are compared to those obtained during other studies in Europe and elsewhere.

Pozvetek

Objavljanje in osnovna analiza obročkovalskih podatkov sta sicer pogosti temi člankov, redko pa so objavljeni podatki iz posameznega mesta, kot je denimo Sombor v premalo raziskani regiji Srbije. Predstavljamo podatke o obročkanju in ponovnem ulovu plavčkov Cyanistes caeruleus in velikih sinic Parus major za obdobje 32 let. Dodatno smo preverili vpliv povprečne najvišje temperature jeseni (september-december) in pozimi (januar-marec) na njihovo številčnost ter pojavljanje v dveh osnovnih habitatnih tipih (parki in vrtovi) v mestu Sombor. Skupno smo obročkali 1675 plavčkov (ponovno ujeti osebki N = 407) in 8062 velikih sinic (ponovno ujeti osebki N = 1517). Pri obeh vrstah so prevladovali mladi osebki (koda EURING 3 oz. 5). Najstarejše obročkane ptice obeh vrst so bile mlajše kot zabeleženo v drugih evropskih raziskavah. Številčnost obeh vrst ni bila povezana s povprečno najvišjo jesensko oziroma zimsko temperaturo. Število obročkanih ptic v parkih in vrtovih se ni pomembno razlikovalo. Glede na ugotovitve predhodnih raziskav sklepamo, da je njihova številčnost v posameznem habitatnem tipu odvisna od razpoložljivost hrane in vremenskih razmer, ne pa drugih okoljskih dejavnikov.

Nest-site characteristics and breeding density of Magpie Pica pica in Sombor (NW Serbia)

In March 2009, active Magpie Pica pica nests were censused in the town of Sombor (Vojvodina, NW Serbia) to study nest-site characteristics, breeding density and spatial distribution. The area of the town can be divided into two parts according to different urban landscapes, i.e. the town centre (150 ha) and the residential area (2,224 ha). In total, 222 Magpie nests were found and their height, tree species and nest-site type determined. Nests were found in 25 tree and two shrub species, the most of them (31.1%) being placed in the commonest tree species in the town, the Common Hackberry Celtis occidentalis. The majority of the nests were found in tree avenues (39.6%) and groups of trees (31.5%). Nests in the town centre with a mean height (± SD) of 15.2 ± 4.05 m were significantly higher than those in the residential area with a mean height (± SD) of 11.4 ± 5.13 m. The mean distance of nests from the top of the canopy (± SD) was 1.5 ± 1.33 m, demonstrating the Magpie's tendency to place its nests in the very tops of trees in the urban areas. In the residential area, nests were present in every height class, while in the town centre they were not found lower than 5 m. This difference can be explained by denser human population in the town centre and hence greater disturbance (e.g. pedestrians), as found in several other studies, but also by the negative effect of high buildings that prevail there. Thus, the height of surrounding buildings, too, might play an important role in nest-site selection in Magpies breeding in urban habitats, especially in densely built-up areas. Breeding density of Magpie in Sombor was 0.94 pairs/10 ha, with almost twice as high in the town centre as in the residential area. The findings of this study are compared to those obtained in other studies in Serbia and abroad.

Abstract

Grasslands host a high diversity of plant and animal species. In Serbia, most alkali grasslands are located in the province of Vojvodina. The majority are not subject to conservation. The aim of the study was to investigate the relationship between the proportion of croplands and (1) the number of breeding species and (2) the number of breeding pairs in the alkali grasslands of the upper Mostonga River catchment basin (NW Serbia). The size of the study area was 400 ha. Birds were surveyed along seven parallel transects eight times per breeding season. Lengths of the cross sections of both grasslands and croplands were measured. The proportion of croplands per transect was calculated by dividing the total length of cross sections of croplands by the total length of transect. The relationship between the proportion of croplands and the number of breeding pairs and the number of breeding species, respectively, was studied using simple linear regression. We recorded a total of 171 nesting pairs belonging to 23 species in the alkali grassland investigated, with breeding densities between 2.2 and 10.3 pairs per 10 ha. The number of species per transect ranged between 6 and 11. The most abundant species were Skylark Alauda arvensis, Yellow Wagtail Motacilla flava and Corn Bunting Emberiza calandra. The numbers of breeding pairs (F6 = 21.761, P < 0.0001) and of breeding species (F6 = 13.758, P = 0.001) were both influenced negatively by the proportion of croplands. These findings highlight the need for coordinated conservation measures on the alkali grasslands of Vojvodina.